Soft tissue closure systems

ABSTRACT

A soft tissue closure system for closing a percutaneous puncture site or soft tissue voids, its method of manufacture and method of use are disclosed. The system comprises a delivery means and a self-expandable, resorbable implant disposed within the delivery means in a compressed configuration. Upon release of the implant member from the system within a soft tissue void, the implant member self-expands to conform to the shape of the soft tissue void and seals the void.

FIELD OF INVENTION

This invention relates generally to the closure of soft tissue siteswith self-expandable, bioresorbable, polymer implants, particularly tothe closure of percutaneous puncture sites. The present invention isalso directed to the delivery of such implants with tubular deliverydevices which penetrate the soft tissue sites to a defined depth forhemostasis and wound closure. Methods of preparing the implants are alsodisclosed.

BACKGROUND OF THE INVENTION

It has been a routine practice to insert a catheter through a puncturesite into a blood vessel to either treat a diseased blood vessel by aprocedure known in the art as percutaneous transluminal angioplasty(PTA), or to deliver systemic drugs to the blood stream forchemotherapeutic applications. In the case of a PTA procedure, anintroducer sheath is inserted into an artery through the puncture sitesuch that a balloon or other type of catheter can then be inserted intothe vessel to carry out the procedure within the vessel. Depending uponthe nature of the disease and the site of arterial insertion, the sizeof an introducer sheath can vary from about 1 mm to as large as about 5mm. One of the complications of these procedures is hemorrhaging at thepercutaneous puncture site after removal of the catheter and theintroducer sheath. In order to stop the bleeding, pressure is applied atthe puncture site until hemostasis occurs. Since the angioplastyprocedures often require the use of anticoagulant, the pressure approachis not always effective and may require a long period of pressurization.

A variety of commercial hemostatic products are available such as thosedisclosed in U.S. Pat. Nos. 2,465,357; 3,742,955; and 3,364,200. A feltor fleece like collagen hemostat is disclosed in U.S. Pat. No.4,066,083. A hemostatic collagen paste comprising a mixture of collagenpowder and saline is disclosed in U.S. Pat. No. 4,891,359. A number ofother collagen based hemostatic materials are disclosed in U.S. Pat.Nos. 4,412,947; 4,578,067; 4,515,637; 4,271,070; 4,891,359; 4,066,083;4,016,877 and 4,215,200. None of these patents teach the art ofhemostasis at a vessel puncture site.

A device to close an arterial puncture site of a blood vessel isdisclosed in U.S. Pat. No. 4,744,364 to Kensey. This device involves theinsertion of an expandable, resorbable material inside of the lumen of ablood vessel via a tubular member which fits inside an introducersheath. A retraction filament is secured to the resorbable material forpulling it to the puncture site so that the resorbable material engagesthe inner surface of the blood vessel contiguous with the puncture. Thefilament is held taut and taped or otherwise secured to patients, skinto hold the resorbable material in position.

The Kensey device introduces several potential risks to the patient. Thedevice may induce an acute thrombosis due to imperfect alignment of thesealing material or to non-hemocompatibility of the material. Thepremature degradation of the filament may leave the sealing materialunsecured, leading to embolization distal to the puncture site. Themigration of the sealing material may not only cause rebleeding, butpotential thrombosis which requires surgical intervention. The potentialrisks involved in such a device may outweigh the benefits such a devicecan offer. Thus, a safe and effective method to close a puncture siteand stop the bleeding is still highly desirable and welcome.

Accordingly, it is the primary object of the present invention toprovide an implant which will close a puncture site and stop thebleeding while substantially reducing the disadvantages and risksassociated with the prior art.

It is a further object of the present invention to provide an implantwhich self-expands in vivo to fill the voids or defects of a tissue ororgan with a biocompatible, resorbable material.

It is still a further object of the present invention to provide amethod to deliver the biocompatible, resorbable implant material totissues or organs of interest by a tubular delivery device.

It is another object of the present invention to provide a means todeliver medicaments, antibiotics, growth factors and other biologicallyactive molecules to selected tissues or organs.

It is yet another object of the present invention to provide a method ofmanufacturing the implant.

SUMMARY OF THE INVENTION

By means of the present invention, a self-expandable, resorbable,hemostatic implant has been discovered which eliminates or substantiallyreduces many of the disadvantages and problems associated with the priorart attempts at closing the punctured wound sites in vesselcatheterization and other soft tissue repair procedures. In addition, bymeans of the present invention, a method is provided to delivermedicaments to the selected site of a soft tissue. More specifically, bymeans of the present invention, a resorbable, self-expandable,hemostatic implant is delivered to a specific vessel puncture site tostop the bleeding in post angioplasty procedures.

The resorbable, self-expandable tissue closure implant of the presentinvention is generally a dry, porous matrix comprised of biologicalfibers. As used herein "biological fibers" include collagen, elastin,fibrin and polysaccharides. In a preferred form of the invention, thematrix is comprised of collagen fibers of animals or humans.

In particular, the self-expandable resorbable implant of the presentinvention comprises a matrix having pores with an average dimension offrom about 100 um to about 3000 um in its fully expanded configuration.

The matrix may also include selected medicaments for local therapeuticapplications. Therapeutic medicaments include, but are not limited to,hemostatic agents such as thrombin, Ca⁺⁺ and the like, wound healingagents such as epidermal growth factor (EGF), acidic and basicfibroblast growth factors (FGFs), transforming growth factors alpha andbeta (TGF alpha and beta) and the like, glycoproteins such as laminin,fibronectin and the like, various types of collagens.

The method for fabricating the resorbable, self-expandable soft tissueclosure implant, in its broadest embodiment, comprises:

a) forming an aqueous dispersion containing biological fibers;

b) pouring the aqueous dispersion into molds;

c) freeze-drying the aqueous dispersion;

d) crosslinking the freeze-dried matrix by treatment with crosslinkingagent;

e) spraying the crosslinked matrix with water mist; and then

f) compressing the water mist treated matrix.

Still further, the invention includes a method for closing a soft tissuepuncture site with the resorbable, self-expandable implant. The methodcomprises delivering the resorbable, self-expandable polymer implant inits compressed configuration to the selected site by a delivery means,particularly a tubular delivery device, and releasing the resorbableimplant at the selected soft tissue site where the resorbable implantself-expands to conform to the soft tissue site to close the defect. Inparticular, the method comprises:

a) inserting a delivery means into the void of the soft tissue to adepth controlled by a depth insertion guide provided on said deliverymeans;

b) ejecting a compressed implant from said delivery means into the void,said implant formed of a material capable of being resorbed in theliving being having an average pore size in the range of from about 100um to about 3,000 um and being self-expandable when wetted, forming anexpanded, hydrated matrix conforming to the shape of and sealing thesoft tissue void; and then

c) removing the delivery means.

The invention also includes a device for sealing a void in a soft tissueof a living being comprising:

a) an implant formed of a material capable of being resorbed in theliving being having an average pore size in the range of from about 100um to about 3,000 um and being self-expandable when wetted;

b) a delivery means having an outlet at its distal end and a depthinsertion guide, said delivery means being adapted to be inserted intothe void to a depth which is controlled by the depth insertion guide,said implant being disposed within said delivery means in a compressedconfiguration; and

c) an ejection means causing the compressed implant to pass out of saidoutlet into the void of the soft tissue to form an expanded, hydratedmatrix which conforms to and seals the soft tissue void.

The resorbable self-expandable, soft tissue closure implant of thepresent invention is constructed such that the matrix is highly porousto provide maximal volume capacity and expansion, and surface area forfluid absorption, platelet adhesion and hemostasis. The highly porousmatrix also provides maximal surface area for cell infiltration andadhesion for wound healing. Thus, in a preferred embodiment of thepresent invention, the self-expandable implant of the present inventionhas the following physical characteristics and physico-chemicalproperties.

    ______________________________________                                        Physical Characteristics:                                                     Diameter of the cylinder (cm)                                                                        1-10                                                   Height of the cylinder (cm)                                                                          0.2-5                                                  Pore size (um)         100-3000                                               Density (g/cm.sup.3)   0.02-0.50                                              Physico-chemical Properties:                                                  Swelling Capacity (g/g)                                                                              2-70                                                   Thermal Shrinkage (°C.)                                                                       50-75                                                  Relaxation Recovery Time (seconds)                                                                   1-30                                                   ______________________________________                                    

The invention will next be described in connection with certainillustrated embodiments.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is the longitudinal cross-sectional view of one embodiment of thepresent invention showing a soft tissue closure system comprising animplant delivery means and an implant positioned therein.

FIG. 2 depicts the use of the system at a percutaneous puncture sitedelivering the resorbable implant in cross-sectional view.

FIG. 3 depicts the resorbable implant in place in cross-section.

DESCRIPTION OF THE INVENTION

Referring now to the figures wherein like reference characters refer tothe same elements, FIG. 1 depicts a soft tissue closure system showngenerally as 10 comprising an implant delivery means 12 and an implantmember 13 disposed within delivery means 12. The primary function ofdelivery means 12 is to deliver implant member 13 at a desired site insitu to effect the filling and closure of a void in the soft tissue of aliving being. In a preferred embodiment, the soft tissue closure systemof the present invention is utilized to effect the closure of a punctureor other opening in a blood vessel, duct or lumen. However, closuresystem 10 may also be utilized for the treatment of wounds resultingfrom other voids created to soft tissue in a living being, typicallysurgeries. Such applications include the filling of voids after removalof malignant tumors, necrotic tissues, deep bullet wounds, knifestabbing, and the like. Voids created by plastic or cosmetic surgery,and the like, are also able to be filled using the closure system of thepresent invention. Still further, the closure system of the presentinvention may also be used to stop the bleeding and fill the voids indiagnostic applications, such as tissue biopsy where a biopsy needle orother biopsy device is utilized.

While the following description and the figures are directed to theclosure of percutaneous punctures in arteries, it should be understoodfrom the above discussion that the present invention has greaterapplicability than this preferred embodiment.

Delivery means 12 is made from any biocompatible material, such asstainless steel; synthetic polymeric materials, such as polyethylene,polypropylene, polyvinyl chloride, polystyrene, polytetrafluoroethylene,polyurethane, or the like; natural polymers, such as collagen, elastin,or the like; and other such biocompatible materials which are well knownto those skilled in the art. Desirably, the delivery means is made frominexpensive, disposable materials, such that it is simply discardedafter use. For ease of manufacture and disposability, synthetic polymersare preferred.

The delivery means shown in the figures comprises a tubular member 11having an outlet 20 at its distal end and an ejector means 22 slidablymounted at the proximal end 28 of tubular member 11. The tubular memberis an elongated body having a depth insertion guide 15, an insertablefront portion 32, and flanged projection 30.

Insertable front portion 32 has a fixed length "y" which is selecteddependent upon the particular soft tissue site that is being repairedand will generally vary from about 2 mm to about 50 mm. It is only thisinsertable front portion 32 of tubular member 11 which actually isinserted into the patient's skin. The depth of insertion is easilycontrolled by the depth insertion guide 15 which is positioned ontubular member 11 at the length "y" such that the tubular member cannotbe inserted past this guide. Guide 15 may simply comprise a partial orfull circumferential projection or ledge which will cause the insertionof the delivery means to stop once the insertable front portion has beeninserted, said ledge then simply resting upon the outermost surface ofthe patient's skin. The shape or design of the guide is not critical aslong as it is capable of controlling the depth of the insertion.

The insertable front portion 32 is preferably constructed of an outsidediameter which is less than the introducer sheath that is used for aparticular intraluminal procedure so as to enable the insertable frontportion 32 to be easily inserted through the skin and be juxtaposed tothe percutaneous puncture site. Depending upon the particularintraluminal procedure, the outside diameter may vary from about 1 mm toabout 5 mm. Except for the insertable front portion 32, the rest oftubular member 11 may have any outside diameter inasmuch as it does notenter the repair site. Desirably, however, for each of construction, theentire tubular member is typically made having the same inside andoutside diameters.

Flanged projection 30 is arranged to be grasped by the fingers of theuser as the implant member 13 is ejected by ejector means 22. Theflanged projection 30 may completely or partially circumscribe tubularbody 11 at its proximal end 28.

The ejector means 22 comprises an elongated, cylindrical rod-like member24 having a push plate 14 attached to its distal end being in a planewhich is perpendicular to its longitudinal axis and a thumb rest 26attached to its proximal end also being in a plane which isperpendicular to the longitudinal axis of rod-like member 24. Push plate14 is disposed inside of tubular member 11, in insertable portion 32,and has an outside diameter which is slightly less than the insidediameter of insertable portion 32 to enable the push plate 14 to traveldown the longitudinal axis of insertable portion 32, to push or forceimplant member 13 out of the outlet 20. Rod-like member 24 is able to beretracted to a distance of "d", as shown in FIG. 1, which distance isonly slightly longer than the length of the implant member 13, so as toensure complete release of the implant and, most importantly, not pushthe implant a distance beyond that which is desired. Thus by controllingthe length "y" of insertable portion 32, the length of the implantmember 13, and distance "d", the implant member 13 is preciselypositioned at the repair site.

In use, the closure system of the present invention is desirablyutilized as soon as possible after the removal of the introducer sheathfrom the puncture site. As shown in FIG. 2, insertable portion 32 isinserted at the repair site through the puncture 42 in skin 40. Depthinsertion guide 15 controls the depth of insertion, stopping the travelof the insertable portion 32 once the guide rests upon skin 40. Toeffect the delivery of the implant member to the repair site, the usergrasps projection 30 with his fingers and places his thumb on rest 26.By applying pressure to the thumb rest, the ejector means travels adistance "d" thereby ejecting implant member 13 and delivering itdirectly over the percutaneous puncture site 42 of vessel 44.

As more clearly shown in FIG. 3, implant member 13 is not positionedinside of the lumen of vessel 44, but rather, by the controlledinsertion depth provided by the present invention, is deliveredextravascularly such that end 46 of the implant member rest outside anddirectly on top of the punctured vessel. The ejected implant member 13expands quickly in situ to completely close the puncture site as thedelivery device is slowly being removed.

FIG. 3 is a schematic representation of a closed puncture site. Theimplant member 13 is shown as having considerably swelled and the bloodaround the implant member has been absorbed and clotted through acollagen induced hemostatic mechanism forming blood clot 50. A woundbandage is shown as 52.

The implantable, resorbable member 13 is made primarily frombiopolymers, such as proteins, polysaccharides or the like. Preferably,a collagen based material is used due to its intrinsic hemostaticproperties.

Type I to type XII collagens may be used either singularly or incombination for the manufacture of the implantable member 13.Preferably, type I collagen is used due to the availability of thismaterial in large quantity, the ease of its isolation and purification,and proven hemostatic properties. The primary source of type I collagenis tendon, skin, bone, and ligament. Both human and animal tissues maybe used to isolate the collagen. In general, animal tissues arepreferred due to easy availability in fresh forms from local slaughterhouses.

In preparing the implantable member 13, type I collagen is firstisolated and purified. A review of the preparation of collagens can befound in "Methods in Enzymology vol. 82, pp. 33-64, 1982". In particularthe collagen of the present invention may be prepared by the followingmethod.

First, a native source of type I collagen, such as skin, tendon,ligament or bone is first cleaned of fat, fascia and other extraneousmatter and washed. The clean and washed collagen containing material isthen comminuted by slicing or grinding. Bone material is subsequentlysubjected to a demineralization procedure. This is achieved either withan acid solution such as hydrochloric acid or a solution of chelatingagent such as ethylenediaminetetraacetic acid (EDTA).

The material is then subjected to a defatting treatment using fatsolubilizing agents such as ethanol, propanols, ethers or a mixture ofether and alcohol. The defatted collagen containing material is thenextracted in a neutral salt solution to remove neutral salt solublematerial. Typically, 1M NaCl solution is used for this purpose. The highionic strength salt solution weakens the non-specifically boundnon-collagenous materials which are solubilized and removed. The saltextracted collagen containing material is then washed with deionized,distilled water.

The neutral salt extracted collagen containing material is thensubjected to an acid extraction in the presence of a structurestabilizing salt to further remove acid soluble non-collagenousmaterials. Applicable acids include acetic acid, lactic acid,hydrochloric acid, sulfuric acid, phosphoric acid, and the like.Regardless of which acid is used, the pH of the acid solution isadjusted to be below 3. The salt used includes sodium chloride, ammoniumsulfate, sodium sulfate, or the like. Acid extraction weakens theinteraction between the collagen and the acidic non-collagenousimpurities which are solubilized and removed.

The acid extracted collagen is then neutralized by adjusting the pH toits isoelectric point at pH of from about 6 to about 7 by adding a base.Applicable bases include sodium hydroxide, potassium hydroxide, ammoniumhydroxide, and the like. By adding a base, the collagen coacervates. Thecoacervated collagen is then filtered by means well known in the artsuch as using a stainless steel mesh filter under vacuum.

The acid extracted, base neutralized collagen is then washed withdeionized, distilled water to remove the residual salt formed by theneutralization procedure. The washed collagen is then subjected to abase extraction in the presence of a structure stabilizing salt. Suchbases are well known in the art such as sodium hydroxide, potassiumhydroxide, calcium hydroxide and the like. Regardless of which base isused, the pH of the solution is adjusted to be above 13. Base extractionweakens the interaction between collagen and the basic non-collagenousimpurities. By adding the base, non-collagenous materials aresolubilized and removed. The base also lowers the isoelectric point dueto a partial deamidation of glutamines and asparagines in collagen whichproduce additional carboxyl groups. The base extracted collagen is thencoacervated by adjusting the pH to its isoelectric point at a pH of fromabout 4.5 to 5.5 by adding an acid to the collagen dispersion so as tofully separate the fibers from the solution for ease of filtration. Suchacids include hydrochloric acid, sulfuric acid, acetic acid, lacticacid, phosphoric acid and the like. The coacervated collagen is thenfiltered. After discarding the extraction solution, the fibers arewashed with deionized, distilled water to remove the residual saltsresulting from neutralization of the extraction solutions. The thuslypurified collagen is stored in a freezer or stored in freeze-dried formfor the preparation of collagen implantable member 13.

To fabricate a collagen implantable member 13, a collagen dispersion isfirst prepared in a manner well known in the art. One such preparationis taught in U.S. Pat. No. 3,157,524, which is incorporated herein byreference as if set out in full. Another preparation of collagendispersion is taught in U.S. Pat. No. 3,520,402 which is alsoincorporated as if set out in full.

In particular, the collagen dispersion of the present invention may beprepared by the following method.

The purified collagen material is first dispersed in 1×10⁻⁴ M NaOHsolution to swell the collagen fibers. The collagen material is thenhomogenized by any conventional means such as with a blender orhomogenizer so as to fully disperse the fibers. The homogenized collagenis then filtered to remove any unswollen aggregates by means well knownin the art such as by passing the dispersion through a stainless steelmesh screen. The pH of the dispersion is adjusted to about 7.4 by adding0.01M HCl. The initial dispersion in a base allows the neutralizationstep to be carried out without passing the isoelectric point so as tonot cause coacervation of the collagen and obtain a more uniformdispersion at pH 7.4. The dispersion is then de aired by vacuum. Theresulting collagen dispersion may then be used to prepare theself-expandable, implantable soft tissue closure device.

Typically, the weight percent of collagen in a dispersion is from about0.5 to about 5.0, preferably in the range from about 1.0 to about 4.0.Higher weight percent of collagen than 5.0 in the dispersion can beobtained by centrifuging the dispersion in a centrifuge and discard thesupernatent. Generally, the higher the centrifugal force applied to thedispersion, the higher the weight percent of collagen in the dispersionafter removing the supernatent.

In one embodiment of the present invention, if the collagen soft tissueclosure system is intended to function as a medicinal delivery vehicle,then in addition to the type I collagen, medicinal additives mayoptionally be included in the dispersion, such as antibiotics, thrombin,polysaccharides such as hyaluronic acid, chondroitin sulfates, alginicacids, chitosan and the like, growth factors such as epidermal growthfactors, transforming growth factor beta (TGF-B) and the like,glycoproteins such as fibronectin, laminin, and the like, type IIthrough type XII collagens, and mixtures thereof.

The collagen dispersion is then poured into molds. The shape of the moldmay be cylindrical, rectangular, spherical or any other shape so long asthe size of the mold is larger than the inner diameter of insertablefront portion 32. For a 2 mm internal diameter (I.D.) insertable frontportion 32, and a cylindrical implantable collagen member 13, thediameter of the mold is preferably in the range of from about 3 mm toabout 15 mm and the height of the mold is from about 3 mm to about 15mm.

The molds containing the dispersion are then placed in a freezermaintained at a temperature of from about -10° C. to about -50° C. for alength of time sufficient to freeze the water present in the dispersion,generally for about 1 to about 24 hours. The frozen dispersion is thensubjected to freeze-drying so as to remove the frozen water. Thisfreeze-drying procedure is carried out in a commercial freeze dryer,such as that manufactured by Virtis, Stokes or Hull, at conditions wellknown to those skilled in the art. Typically, the vacuum within thedrying chamber is maintained at from about 50 um to about 300 um of Hg,at a temperature of from about -10° C. to about -50° C. for about 16 toabout 96 hours. The temperature is then raised to about 25° C. for about3 to 24 hours.

The freeze-dried, highly porous collagen matrix is then subjected to acrosslinking process to introduce additional intermolecular crosslinksto stabilize the form of the collagen matrix. The crosslinking iscarried out by means well known in the art. Any reagents which canchemically react with amino groups, hydroxyl groups, guanidino groups,carboxyl groups that can link the side chains of different collagenmolecules ma be used to crosslink the collagen matrix. This can beaccomplished with chromium sulfate, formaldehyde, glutaraldehyde,carbodiimide, adipyl chloride, hexamethylene diisocyanate and the like.The rate of in vivo resorption of the collagen is dependent upon thedegree of intermolecular crosslinking in the collagen matrix. Factorscontrolling the extent of crosslinking are the type and concentration ofthe crosslinking agent; the pH, time and the temperature of incubationin the liquid phase; or the vapor pressure of the crosslinking agent,time, temperature and the relative humidity when carrying outcrosslinking in the vapor phase. Desirably, the collagen matrix of thepresent invention is crosslinked to the extent that the collagen iscompletely resorbed within about 2 to about 10 weeks.

Appropriate crosslinking of the freeze-dried matrix introduces severalvery important properties of the present invention for the specifiedmedical application as a soft tissue closure device. Effectivecrosslinking locks in the physical geometry of the matrix which isdefined by the shape of the mold. Consequently, the matrix behaveselastically when a stress is applied to the matrix. That is, when thematrix is deformed or compressed physically, it will return to itsoriginal form and size upon relaxation or release of the externalstress. This elastic behavior of the appropriately crosslinkedfreeze-dried collagen matrix is especially manifested when the collagenmatrix is in the wet state, as when it absorbs blood at the puncturesite. This is a result of hydrophilicity and the Donnon osmotic pressureof the collagen matrix. The recovery time from the deformed orcompressed state to the original shape in the wet state is as short asfrom about 1 second to about 30 seconds. Desirably, the recovery time isfrom about 3 to about 10 seconds.

Another important property caused by crosslinking the collagen matrix isits solution uptake capacity, or the blood absorption capacity, whenutilized to seal the puncture site and induce hemostasis. The solutionuptake of the crosslinked collagen matrix of the present invention islimited by the size of the mold which defines the total volume of thematrix of the present invention. The total volume of a matrix is definedby the geometry of the mold. Typically, when the mold is of the form ofa cylinder, the volume is defined by the area of the base of thecylinder and the height of the cylinder. The desirable volume of thematrix when in use for puncture site closure is dependent upon theparticular size of the introducer sheath used. Particularly, when a 9F(about 3 mm) introducer sheath is used, the desirable dimension of acylindrical matrix is to have a base dimension of from about 4 mm toabout 15 mm, and a height of from about 2 mm to about 10 mm.

Yet an additional property controlled by crosslinking the collagenmatrix is its density. Dependent upon the particular puncture site to berepaired and the physical, chemical and biological requirements, thedensity of the matrix in the fully expanded configuration may vary fromabout 0.02 gram matrix material per cubic centimeter of the matrixvolume to about 0.5 gram matrix per cubic centimeter matrix volume.Typically, to close a puncture sites from angioplasty procedures, thedensity of the matrix in the fully expanded configuration varies fromabout 0.02 gram matrix/cm³ to about 0.15 gram matrix/cm³.

The degree of crosslinking of the collagen matrix of the presentinvention can be measured by the hydrothermal shrinkage temperature(T_(s)) of the matrix, i.e. the onset temperature at which the matrixbegins to shrink in its dimension in an aqueous environment as a resultof the unwinding of the triple helical structure of the collagenmolecules. The methods for measuring the shrinkage temperature of amaterial is well known in the art, such as by a differential scanningcalorimeter, or by measuring the dimensional change using acathetometer.

Generally, the degree of crosslinking is such that the shrinkagetemperature of the collagen matrix is in the range of from about 50° C.to about 75° C., preferably from about 55° C. to about 65° C.

In one embodiment of the present invention, the collagen matrix iscrosslinked with formaldehyde vapor. Either commercial formaldehydevapor, or vapor of formaldehyde generated from a formaldehyde solutionmay be used. Particularly, the crosslinking is conducted in a chamberwith a relative humidity in the range from about 80% to about 100%,preferably in the range from about 85% to about 95%, and in the presenceof an excess amount of formaldehyde vapor, at a temperature of about 25°C. for a period from about 30 minutes to about 8 hours. Specifically,crosslinking by formaldehyde vapor generated from 1% formaldehydesolution at 25° C. and at 95% humidity for 60 minutes produces acollagen matrix of a shrinkage temperature of from about 55° C. to about65° C. for a matrix of density from about 0.02 g/cm³ to about 0.15 g/cm³in the fully expanded configuration.

The crosslinked collagen matrix is then subjected to a water misttreatment. Any commercial water mist sprayer is suitable for thispurpose. The collagen matrices are sprayed for about 10 seconds to about60 seconds while the collagen matrices are being tumbled in a containerat about 25° C. The water mist treated matrices are then equilibrated ina closed container for about 30 minutes to further soften the matricesfor the compression step which follows. As a result of this watertreatment, the collagen matrices have a water uptake of about 10 to 40%by weight, based on the weight of the dry material. The water misttreated collagen matrix is then subjected to mechanical compression toreduce its size in order to fit into insertable portion 32.Particularly, when the matrix is in a cylindrical form, the mechanicalcompression is applied in the radial direction such that the base areais reduced to approximately the size of the I.D. of insertable portion32. Generally, the compressed collagen matrix has a volume of from about1/100 to 1/3 of the non-compressed matrix. The compressed collagenimplantable member 13 is then inserted into insertable front portion 32.At this point, the loaded soft tissue closure system is individuallypackaged for sterilization.

The crosslinking of the matrix, the water mist treatment and themechanical compression are important aspects of the present invention.More importantly, the sequence of operation as described in thisinvention is critical in providing the desirable properties of thecollagen matrix. The density, the pore structure and the extent ofswelling of the compressed collagen implant member is directly relatedto how the collagen matrix material was made. For example, a change ofthe order from the present invention to water mist treatment, mechanicalcompression and then crosslinking the matrix will result in a matrixwhich will not self-expand when the stress is released and which doesnot have the blood absorption capability.

While only the sealing of a percutaneous puncture seal has beendiscussed as an example to describe the present invention, it will beunderstood that various changes, modifications, and applications may bemade without departing from the scope and the spirit of the presentinvention.

The above and other objectives, advantages and features of the presentinvention will be better understood from the following examples.

EXAMPLE 1 Preparation of the Collagen Dispersion

The fat and fascia of the bovine flexor tendon are carefully cleaned andremoved and washed with water. The cleaned tendon is frozen anddiminuted by slicing into 0.5 mm slices with a meat slicer. The tendonis first defatted with isopropanol (tendon:isopropanol=1:5 v:v) for 8hours at 25° C. under constant agitation. The extraction solution isdiscarded and equal volume of isopropanol is added and the tendon slicesis extracted overnight at 25° C. under agitation. The tendon is thenextensively washed with deionized, distilled water to remove theresidual isopropanol. The defatted tendon is then extracted with 10volumes of 1M NaCl for 24 hours at 4° C. under agitation. The saltextracted tendon is washed with deionized, distilled water. The fibersare next extracted with 10 volumes of 0.6M NaOH for 24 hours at 25° C.in the presence of 1M Na₂ SO₄ under constant agitation. The alkalineextracted collagen is then collected by filtration and neutralized with0.1M HCl and the fibers collected, washed to remove the residual saltand frozen.

An aliquot of the above purified fibers is first suspended in 1×10⁻⁴ MNaOH solution. The amount of fibers and base solution used is such thata 1.5% (w/v) of collagen suspension is reached. The swollen fibers arethen homogenized in a stainless steel blender for 60 seconds. The thuslydispersed collagen material is filtered through a 40 um stainless steelmesh. The pH of the dispersion is then adjusted to about 7.4 by adding0.01M HCl. The dispersed material is then de-aired by vacuum and storedat 4° C. until use.

EXAMPLE 2 Preparation of collagen Soft Tissue Closure Implant

Collagen dispersion prepared from Example 1 is poured into stainlesssteel molds of 10 mm in diameter and 5 mm in height. The collagencontaining molds are then subjected to a freeze-drying procedure using aVirtis commercial freeze dryer. The conditions for freeze-drying are:freeze at -40° C. for 6 hours; drying at 150 um Hg at -10° C. for 24hours followed by drying at 25° C. for 8 hours. The freeze-driedcollagen matrices are then subjected to a formaldehyde vaporcrosslinking in a crosslinking chamber containing excess amount offormaldehyde vapor (generated by a 1% formaldehyde solution at 25° C.),95% relative humidity at 25° C. for 60 minutes. The crosslinked collagenmatrices are sprayed with water mist for 10 seconds and equilibrated ina closed container for an additional 30 minutes. The water mist treatedmatrices are then compressed by rotating between two glass plates with agap of 2.5 mm such that the diameter of the 10 mm sponge matrix reducesto about 2.5 mm. The compressed collagen matrix is then inserted into aprefabricated implant delivery means of 2.5 mm I.D. and 3.0 mm O.D.(member 11, FIG. 1).

EXAMPLE 3 Preparation of collagen soft Tissue Closure Implant in thepresence of thrombin

The collagen dispersion from Example 1 is mixed uniformly with thrombin(collagen:thrombin=10:1 w/w). The thoroughly mixed collagen/thrombin gelis then poured into the stainless steel molds as in Example 2. Thesubsequent steps are identical to the Example 2.

EXAMPLE 4 Characterization of Collagen Soft Tissue Closure Implant

a) Density (g/cm³)

The apparent density of the soft tissue closure implant in the fullyexpanded configuration is determined by first weighing the collagenmatrix to obtain the dry weight. The volume of the matrix is thendetermined from the radius and the height of the sponge according to:V=II×r² ×h, where r is the radius and h is the height of the matrix. Thedensity of the collagen oft tissue closure implant of the presentinvention is in the range of from about 0.02 g/cm³ to about 0.5 g/cm³.

b) Swelling (g/g)

The swelling is measured by the amount of solution uptake per unitweight of the soft tissue closure device. The dry weight of the collagenmatrix is first determined. The collagen matrix is next immersed in abuffered solution at pH 7.4 at 25° C. for 5 minutes. The wet weight isthen determined. The swelling (g/g) of the collagen matrix is calculatedas the difference of wet weight and dry weight of the matrix divided bythe dry weight of the matrix. The swelling capacity of the collagen softtissue closure implant of the present invention is in the range of fromabout 2 g/g to about 70 g/g.

c) Pore Size (um)

The pore size is obtained from the scanning electron microscopy ofcross-sections of the collagen implant in its fully expandedconfiguration. The pore size of the collagen matrix of the presentinvention is in the range of from about 100 um to about 3000 um.

d) Relaxation Recovery Time (seconds)

The collagen soft tissue closure implant of the present invention in itscompressed configuration is pushed out from the disposable deliverymeans into a buffered solution, pH 7.4 at 25° C. The compressed matrixis relaxed and hydrated and self expanded to the original fully expandedconfiguration. The time it takes to recover to the fully expandedconfiguration is recorded. The relaxation recovery time for the presentinvention is in the range of from about 1 second to about 30 seconds.

e) Shrinkage Temperature (°C.)

A 10 mg of the collagen matrix is first wetted in a buffered solution,pH 7.4. The sample is sealed into an aluminum sample pen and insertedinto a sample holder of a differential scanning calorimeter. The buffersolution is used as a reference. The heating rate is 5° C./min. Theshrinkage temperature is defined as the onset of the endothermic peakfrom the heat capacity versus temperature plot. The thermal shrinkagetemperature of the collagen soft tissue closure implant of the presentinvention is in the range of from about 50° C. to about 75° C.

EXAMPLE 5 Method of Use of a Collagen Soft Tissue Closure Implant

An appropriately sized collagen soft tissue closure implant is insertedinto a puncture site immediately after the introducer sheath is removed.The collagen implant is ejected into the puncture site and allowed to befully hydrated and self-expanded in situ for 5 minutes. The disposabledelivery means is then slowly withdrawn. Slight pressure is then appliedto the wound for 5 to 10 minutes to ensure complete hemostasis and woundclosure.

EXAMPLE 6 Method of Use to Close a Soft Tissue Site

An appropriately sized delivery means is inserted through a percutaneoussite to the tissue site of interest. The collagen implant is then pushedout of the tubular delivery means via a piston to the tissue site whilethe delivery means is slowly being withdrawn. The collagen implant selfexpands to fill the voids of the soft tissue site.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or essential characteristics thereof. Thepresent embodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescriptions.

What is claimed is:
 1. A device for sealing a void in a soft tissue of aliving being which comprises:a) an implant, having a length comprised ofcollagen material which is capable of being resorbed in the living beingcharacterized by being in a compressed configuration and self-expandablewhen wetted to contain an expanded average pore size of from about 100μm to about 3,000 μm, said implant having a relaxation recovery time offrom about 1 second to about 30 seconds and having a volume in itscompressed configuration state which i from about 1/100 to about 1/3 ofthe volume of its expanded state and is formed by the stepscomprising:(i) forming an aqueous dispersion containing collagen; (ii)pouring the aqueous dispersion into molds; (iii) freeze drying theaqueous dispersion to form a collagen matrix; (iv) crosslinking thecollagen matrix by treatment with crosslinking agent; (v) spraying thecrosslinked collagen matrix with water mist; and then (vi) compressingthe water mist treated collagen matrix; b) a delivery means having anoutlet at its distal end and a depth insertion guide, said deliverymeans being adapted to be inserted into the void to a depth which iscontrolled by the depth insertion guide, said implant being disposedwithin said delivery means; and c) a retractable ejection means capableof ejecting the compressed implant out of the said outlet a controlleddistance into the void of the soft tissue to form an expanded, hydratedmatrix which conforms to seal the soft tissue void, wherein (i) thedepth insertion guide, (ii) the length of the implant, and (iii) theretractable ejection mans, in combination, control the positioning ofthe implant within the void.
 2. The device of claim 1, wherein the selfexpandable resorbable implant is formed of a biocompatible,bioresorbable material.
 3. The device of claim 2, wherein thebiocompatible bioresorbable material is type I collagen.
 4. The deviceof claim 1, wherein the delivery means is a tubular member having alongitudinal axis and wherein the ejection means comprises a pushermember located within the tubular member and arranged to move down thelongitudinal axis to force the implant out of the outlet.
 5. The deviceof claim 4, wherein the delivery means is formed of a biocompatiblematerial.
 6. The device of claim 5, wherein the biocompatible materialis a synthetic polymeric material.
 7. The device of claim 5, wherein thebiocompatible material is a metallic material.
 8. The device of claim 1,wherein the implant self expands to comform to the tissue void when incontact with body fluid.
 9. The device of claim 1, wherein the implantis of any geometrical shape.
 10. The device of claim 1, wherein thedepth insertion guide comprises a projection extending outwardly fromthe longitudinal axis of the delivery means, the distance between theprojection and the outlet defining the depth of insertion of thedelivery means.
 11. The device of claim 1, wherein the implant has adensity from about 0.02 g/cm³ to about 0.50 g/cm³ in the fully expandedconfiguration, a solution uptake capacity of from about 2 g/g to about70 g/g, a shrinkage temperature from about 50° C. to about 75° C., and arelaxation recovery time from about 1 second to about 30 seconds. 12.The device of claim 1, wherein the resorbable implant further containsmedicaments selected from the group consisting of antibiotics, growthfactors, thrombin, glycosaminoglycans, prostaglandins, type II throughtype XII collagens, glycoproteins, fibronectin, laminin and mixturesthereof.